1. Field of the Invention
The present invention relates to a crimping terminal, particularly to a crimping terminal which can suitably connect with an aluminum or aluminum alloy electric wire.
2. Description of the Related Art
In the conventional wiring harness arranged in a vehicle such as a motor vehicle, generally copper electric wires are used as a conductor. The copper wires are made of copper material having superior electrical conductivity, and manufactured at low cost. An aluminum electric wire (including an aluminum alloy electric wire) is not used often as a conductor since characteristic of conductive property and intensity is less than the copper wire. However, in recent years, automotive lightening is desired so as to achieve low fuel consumption from strong request against environmental issues. Also, wishes regarding use of an aluminum electric wire are increasing in the automotive industry.
Meanwhile, density of an aluminum electric wire (density of aluminum is 2.7 g/cm3) is about one third lighter than a conventional useful copper electric wire (density of copper is 8.96 g/cm3). However, mechanical strength of aluminum is low. In addition, the surface of conductor of aluminum is susceptible to oxidation. As a result, oxidized aluminum, that is, oxide layer is formed on the surface. The oxide layer is a very thin layer, but has an insulation property. Thereby, when the aluminum electric wire in which the oxide layer was formed is connected, there is a problem such that electric resistance becomes high. For this reason, it is required to remove the oxide layer from the surface of aluminum electric wire when the aluminum electric wire is connected. Especially, in case of aluminum electric wire for operating at a low voltage such as a signal wire, removal of the oxide layer is important so as to conduct electricity certainly.
A crimping terminal is known as a connecting terminal for connecting an aluminum electric wire to a non-terminating portion of a vehicle. The crimping terminal has a locking portion and a crimping part. The locking portion is connected to the non-terminating portion and formed in one end of the crimping terminal. The crimping part is connected to the aluminum electric wire and formed in another end of the crimping terminal. This kind of the crimping terminal for using an aluminum electric wire has a U-shaped crimping part in which a slanting serration is formed on the inside. When the aluminum electric wire is crimped, the oxide layer formed on the surface of conductor is destroyed by the serration and connected (for example, see the patent document 1: Japan published patent application 2003-249284). Also, an electric wire connecting terminal described in the patent document 2 is known. The electric wire connecting terminal of the patent document 2 (Japan published patent application 2004-14216) has an insertion hole, a terminal of male screw side, and a terminal of female screw side. An aluminum electric wire is inserted into the inset hole. In the terminal of male screw side, the male screw is formed on an outer circumference. In the terminal of female screw side, the female screw for screwing the male screw is formed. By rubbing the conductor against the screw formed in an inner wall of the insertion hole and screwing the screw, the oxide layer is destroyed. Thereby, the electric wire is connected.
The crimping terminal for aluminum electric wire disclosed in the patent document 1 mounts a conductor of aluminum electric wire on the crimping part formed in a U-shaped, bends an end portion of thereof, and then is crimped to the conductor. Thereby, when the exposed conductor is long, a part thereof protrudes from the crimping terminal for aluminum electric wire easily. Additionally, the part may come into contact with nearby other components.
On the other hand, in the electric wire connecting terminal described in the patent document 2, a conductor of aluminum electric wire is inserted into the insertion hole, and then is crimped and fixed. Thereby, a part of the conductor little protrudes from the electric wire connecting terminal. However, components are large, and shape of components is complex. As a result, it causes increase in cost by additions of components. Furthermore, there is room for improvement.
In addition, the crimping terminals of both the patent documents 1 and 2 have not processing function of the oxide layer (specifically, dust of the oxide layer) removed from the conductor. As a result, the dust of oxide layer goes in between the conductor and the crimping surface of the crimping terminal. Thereby, electric resistance may become high.